Process for making beta-lactam polymers



United States Patent Int. Cl. C08g 20/10 US. Cl. 260-78 19 ClaimsABSTRACT OF THE DISCLOSURE A process for making beta-lactam homopolymersand copolymers is disclosed which provides an improved control of thedegree of polymerization and the distribution of molecular weight. Inthe case of the copolymers, it makes possible a statistical distributionof monomeric units with monomers having substantially dilferent reaction rates. The beta-lactams used have a hydrogen atom at the nitrogenatom thereof and from 0 to 4 substituents on the alpha and/ or betacarbon atoms thereof. Polymerization may be effected at a temperature of-l5 to 120 C. by anionic polymerization in a polymerization reactionmixture comprising a solution or dispersion of a basic catalyst in aninert solvent. The desired control is achieved by feeding the lactammonomer incrementally and slowly to the polymerization reaction mixture,i.e., at a rate substantially equal to the rate at which it reacts toform the polymer.

The present invention relates to a process for preparing lactamhomoploymers and copolymers. This application is a continuation-in-partof our prior applications Ser. Nos. 518,988 and 519,016 both filed onJan. 6, 1966, now abandoned.

In the anionic polymerization of lactams according to known methods, abasic catalyst and, if desired or required, a chain starting agent, areadded to the lactam. At a certain temperature, which depends on thenature of the starting monomers used, polymerization is initiated andproceeds until a certain degree of conversion is attained, whereupon itslowly ceases. In general, beta-lactams are also polymerized accordingto the same principle in a homogeneous phase or in dispersion. In suchpolymerizations it is customary to use solvents which dissolve thelactam and swell or dissolve the polymer that forms.

When proceeding in this manner it is often difficult, because of theheat of the reaction, to control the polymerization which sets in. It isalso difficult to influence the distribution of the molecular weight ofthe polymers formed. Moreover, in the case of copolymers, if thepolymerization rates of the lactam monomers are very different, anon-homogeneous product is obtained having the character of a blockcopolymer. Using known processes copolymers with a statisticaldistribution of the different monomeric units in each individual chainmolecule is possible only if the monomeric lactams used polymerize underthe same conditions at substantially the same speed.

The present invention is based on the discovery that the aforesaiddisadvantages can be avoided and that betalactam polymers having aregulated distribution of ice molecular weight, and in the case ofcopolymers a statistical distribution of monomeric units, can beobtained by establishing a polymerization reaction medium comprising aninert solvent solution or dispersion of a basic catalyst and addingthereto the lactam or lactams to be polymerized, incrementally i.e.,either continuously or in small increments, at a relatively slow rate.The feed rate should be slow enough to prevent any substantialaccumulation of unreacted monomers in the reaction medium and isdesirably substantially equal to the rate at which the monomers areconsumed in the polymerization reaction. In cases where copolymers areto be made from beta-lactams having difierent reaction rates, the feedrate is adjusted in relation to the slowest reacting monomer to avoidaccumulation of unreacted monomer in the reaction medium. When thequantities employed are small, drop-by-drop addition of the monomers maybe used. It has been found that generally the monomer or monomer mixtureshould be'fed to the polymerization reaction medium over a period of atleast about 45 minutes.

It is surprising that the degree of polymerization and the distributionof the molecular weight can be modified to a very large extent in thedesired way by slowly adding the monomer at the same rate at which it isconsumed, to a solution or dispersion of the basic catalyst during thepolymerization instead of combining the total amount of monomer from thebeginning in a definite ratio with the catalyst. The former method ofoperation has the following advantages over the known methods ofpolymerizing beta-lactams:

(1) The degrees of polymerization that can be obtained are much higherthan those that can be obtained by the known processes.

(2) The distribution of the molecular Weight can be modified within verywide limits in the desired way.

(3) Even in cases in which relatively large quantities of materialcontaining quickly polymerizing beta-lactams are involved, it is notdifiicult to dissipate the heat during the polymerization process, sincethe speed at which the monomer is added can be regulated in the desiredway to control the rate of heat generation.

(4) Since according to the invention lactam and catalyst are introducedseparately into the reaction vessel, even if the polymerization iscarried out in disperse phase, mixing devices which clog easily duringthe polymerization, in particular in cases in which quickly polymerizingbeta-lactams are present, and which must be thoroughly cleaned betweeneach run in the usual polymerization process, can be dispensed with whenthe lactam is fed to the catalyst solution according to the presentinvention.

'(5) In the case of copolymers, by feeding two or more lactams, eitherseparately or in admixture with one another, and in a predeterminedratio, sufliciently slowly to the reaction mixture, copolymers having astatistical distribution of monomeric units are obtained, even thoughthe polymerization rates of the several monomers ditfer substantially.

(6) By feeding the monomer or monomers at the same rate as that at whichthey polymerize, a constant ratio of chain-starting andchain-interrupting reactions can be established over the reactionperiod. In this way the distribution of molecular weight can be modifiedand polymers with a narrow and uniform distribution of molecular weightobtained.

According to the process of the invention there may be polymerized allbeta-lactams which are unsubstituted at the nitrogen atom and carry, inthe alphaand betapositions with respect to the carbonyl group from zeroto four substituents containing a total of up 0 l2 aliphatically boundcarbon atoms or an aromatic radical and up to 9 3 aliphatically boundcarbon atoms for a total of carbon atoms. As indicated below, thesubstituent carbon atoms may comprise a ring including the alpha andbeta carbon atoms of the lactam.

Suitable lactams are, for example, azetidinone, 4-methyl azetidinone,4-isopropyl azetidinone, 4-vinyl azetidinone, 4-phenyl azetidinone,4-methyl-4-phenoxymethyl azetidinone, 4-chloropheny1 azetidinone,3,3-dimethyl azetidinone, 3,4-dimethyl azetidinone, 4,4-dimethylazetidinone, 4-methyl-4-neopentyl azetidinone, 3,3,4,4tetramethylazetidinone, 4-(4-isopropyl cyclohexyl)-azetidinone or polycycliclactams of the constitutions Mixtures of beta-lactams containing up to50% of higher lactams, for example, alpha pyrrolidone, can also be usedin the process of the invention.

Polymerization is carried out according to the anionic reactionmechanism using a solution or dispersion of a basic catalyst. It iscatalyzed in usual manner by the addition of alkaline compoundsproducing lactam anions in the polymerization batch. Suitable substancesare, for example, the alkali metal compounds of beta-lactams, thepotassium salt of pyrrolidone, the sodium salt of e-caprolactam, phenylsodium, lithium hydride and other catalysts used in anionic lactampolymerization.

If desired, chain starting agents such as N-acyl or N-sulfonyl compoundsof lactams can be used in known manner. It is likewise possible toproduce the chain starting agent in the polymerization batch by addingacylating or sulfonating reagents.

In general, anionic polymerization is carried out at a temperature inthe range of from -15 C. to +120 C.

The process according to the invention permits a much greatermodification of the degree of polymerization and of the molecular weightdistribution than known processes. A different distribution of themolecular weight can be obtained, for example, by first introducing, inone case, an acyl lactam active as chain starting agent, and, in anothercase, feeding it together with the monomer. According to the lattermethod products can be obtained having an especially broad molecularweight distribution. When, simultaneously with the lactam, chainstarting agents and a metered small amount of chain interrupting agents,for example water, are added, products are obtained, the molecularweight distribution of which is not so broad. The properties of thepolymer that is formed can also be modified by the feed rate or theamount of catalyst. It is especially advantageous to regulate the feedrate in such a manner as to prevent the building up of a concentrationof unreacted monomer in the reaction vessel.

The polymerization process according to the invention can be carried outin most of the customary organic solvents. It is particularlyadvantageous to use solvents which are capable of swelling or dissolvingthe forming polymer, for example, dimethyl sulfoxide, tetramethylenesulfone, phosphoric acid tris-dimethyl amide, dimethyl formamide ormethyl pyrrolidone. In these solvents the highest degrees ofpolymerization are obtained.

Owing to the fact that towards the end of the monomer addition thereaction mixture becomes more and more viscous and may finally solidifyto a gel, considerable mechanical effort may be required to achieveduniform distribution of the feed monomer or monomers throughout thereaction mixture. In order to avoid these and other difficulties in thepolymerization, the catalyst solution is preferably emulsified in adifferent second solvent with which it is essentially immiscible ormiscible to only a limited extent so that two separate solvent phasesare formed. As outer phase solvents there can be used, for example,those that are practically immiscible or incompletely miscible with thelactam and the solvent of the catalyst solution. As a dynamicequilibrium exists between the droplets of an emulsion, the lactam beingfed gradually infiltrates in disperse form into the entire inner phaseand finally it is completely polymerized. Owing to the fact that thisdistribution process may be too slow, especially with more rapidlypolymerizing beta-lactams, droplets in which the polymerization takesplace may be depleted of monomers so that very different products can beobtained depending on the stirring speed and the size of the droplets.Finally, after a certain conversion, the exchange of material betweenthe droplets of a polymerization emulsion may come to a standstill (cf.Houben- Weyl, Methoden der Organ. Chemie, 4th edition, volume 14/1, p.409).

It is, therefore, particularly advantageous to use as the outer phasesolvents that are incompletely miscible with the catalyst solution andcompletely miscible with the lactams or lactam mixtures to bepolymerized. In such cases the added lactam diffuses in the form of amolecular dispersion through the outer phase into the droplets of thecatalyst solution so that the solution equilibrium is obtained veryrapidly. In this manner high viscosities can be attained, for example.

Suitable solvents for preparing the catalyst solution, which commonlyforms the inner phase, are dimethyl sulfoxide and tetramethylenesulfone. These solvents are incompletely miscible with all disclosedsolvents of the outer phase. When aliphatic hydrocarbons are used asouter phase, dimethyl formamide and methyl pyrrolidone are also suitablefor the catalyst solution.

As solvents for the outer phase which are miscible neither with thebeta-lactams specified above nor with the solvents of the catalystsolution there can be used aliphatic or cyclo-aliphatic hydrocarbonshaving 5 to 25 carbon atoms.

As solvents for the outer phase which are completely miscible with mostof the beta-lactams or the mixtures thereof, but are miscible to alimited extent only with the solvents of the catalyst solution, therecan be used, for example,

(1) aliphatic ethers having 1 to 5 ether oxygen atoms and 4 to 24 carbonatoms in the molecule;

(2) araliphatic ethers having 1 to 3 ether oxygen atoms, 6 to 24aliphatically bound carbon atoms and 1 to 3 phenyl rings in themolecule;

(3) araliphatic hydrocarbons with l to 3 phenyl rings and 3 to 24aliphatically bound carbon atoms in the molecule.

Mixtures of the aforesaid solvents may also be used.

In order to produce an emulsion that is as fine as possible andespecially favorable for polymerization reaction, it is advantageous toadd to the polymerization reaction medium emulsifying auxiliaries, suchas emulsifiers, protective colloids or thickening agents.

The following examples serve to illustrate the invention but they arenot intended to limit it thereto.

EXAMPLE 1 A soluion of grams of 4-methyl-azetidinone and 36 milligramsof oxalyl pyrrolidone in 200 cc. of dimethyl sulfoxide was dropped at 20C., in the course of 1 hour, while stirring intensely, into a dispersionof 2.4 grams of the potassium salt of pyrrolidone in 1500 cc.

of dimethyl sulfoxide. The reaction mixture became more and more viscousand finally solidified in gel form. After another hour the mixture wasfinally triturated with water, sucked off and dried. 95 grams of apolymer having a relative viscosity of 46.0 (measured at 20 C. in asolution of 1 gram of substance in 100 cc. of concentrated sulfuricacid) were obtained. Similar products were obtained when phosphoric acidtris dimethyl amide was used as the solvent.

When the polymerization was repeated under the same polymerizationconditions, the only difference being that all reaction components werecombined within one minute, the product obtained had a relativeviscosity of 13.5.

EXAMPLE 2 A solution of 3 grams of the potassium salt of pyrrolidone in600 cc. of dimethyl sulfoxide, to which 6 cc. of 4,4-dimethylazetidinone were added as a dissolving intermediary, was emulsified in900 cc. of kerosene boiling within the range of 160 to 180 C. andcontaining 0.5% of an ethylene-propylene dimethyl sulfamide of theformula [C H SO N(CH Cl and 0.05% of polyisobutylene.

Into the resulting emulsion a solution of 0.15 gram of oxalylpyrrolidone in 300 grams of 3,4-dimethyl azetidinone was slowlyintroduced drop by drop in the course of two hours. When theintroduction of the solution was terminated stirring was continued foranother 4 hours. The fine-grained bead polymer which could well besucked off was freed from the adhering solvents by being boiled withwater. The product (279 grams) had a relative viscosity of 12.8(measured at 20 C. in a solution of 1 gram of substance in 100 cc. ofconcentrated sulfuric acid).

When dimethyl formamide was used instead of dimethyl sulfoxide theproduct obtained had a relative viscosity of 11.8.

When the polymerization was carried out under the, same conditions, theonly difference being that all reaction components were combined withinone minute, the reaction product obtained had a relative viscosity of7.5.

EXAMPLE 3 A solution of 3 grams of the potassium salt of pyrrolidone in600 cc. of dimethyl sulfoxide to which 6 cc. of 4,4-dimethyl azetidinonewere added as a dissolving intermediary was emulsified in 600 cc. ofisopropyl ether which contained 0.5% of an emulsifier of the typedescribed in Example 2. Into the resulting emulsion a solution of 300grams of 4-methyl azetidinone and 0.15 gram of oxalyl pyrrolidone in 300cc, of isopropyl ether was introduced drop by drop in the course of 1hour at 20 C., while stirring vigorously. After washing out and dryingthe fine-grained reaction product 288 grams of a polymer having arelative viscosity of 23.6 (measured at 20 C. in a solution of 1 gram ofsubstance in 100 cc. of concentrated sulfuric acid) Were obtained.

When all reaction components were combined within one minute underotherwise the same conditions, it was impossible, despite intensecooling, to keep the reaction temperature below 50 C. The polymer thusobtained had a relatively viscosity of 5.5.

When all the reaction components were used in quantities correspondingto one-third of the quantities indicated above in this example and whenthese components were combined within one minute, the reactiontemperature could be kept below 30 C. and a polymer having a relativeviscosity of 7.5 was obtained.

EXAMPLE 4 A solution of 2 grams of the potassium salt of pyrrolidone in400 cc. of dimethyl sulfoxide to which 4 cc. of 4,4-dimethyl azetidinonehad been added as a dissolving intermediary was emulsified in 400cc. ofisopropyl ether which contained 0.5% of an emulsifier of the kinddescribed in Example 2. Into the resulting emulsion a solution of 200grams of 4-methyl azetidinone, 0.1 gram of oxalyl pyrrolidone and 0.3gram of water in 200 cc. of isopropyl ether was introduced drop by dropat 20 C. in the course of one hour, while stirring vigorously. Afteranother hour the fine-grained product was sucked off, boiled with waterand dried. 180 grams of a polymer having a relative viscosity of 10.5(measured at 20 C. in a solution of 1 gram of substance in cc. ofconcentrated sulfuric acid) were obtained. As the polymer of a relativeviscosity of 23.6 which had been obtained according to Example 3 theproduct obtained according to the present example could be cast intofilms from a formic acid solution. The two products differed from oneanother, however, very clearly in the tendency of their solutions tocoagulate and in the drawability of the films prepared from them.

EXAMPLE 5 A solution of 0.5 gram of the potassium salt of pyrrolidoneand 15 milligrams of oxalyl pyrrolidone in 100 cc. of tetramethylenesulfone was emulsified in cc. of i-dodecyl benzene which contained 0.5%of the emulsifier used in Example 2. Into the resulting emulsion amixture of 50 grams of 4-vinyl azetidinone and 50 cc. of i-dodecylbenzene was introduced drop by drop at 30 C. in the course of one hour.After another hour the product was sucked off, washed with acetone,triturated with water and sucked off. 48 grams of a polymer wereobtained. A solution of 1 gram of the product in 100 cc. of concentratedsulfuric acid had a relative viscosity of 22.3.

EXAMPLE 6 0.02 gram of oxalyl pyrrolidone was added to a dispersion of0.3 gram of the potassium salt of pyrrolidone in 200 cc. oftetramethylene sulfone. Over a period of 1 hour at 30 C. a mixture of 10grams of 4-phenyl-azetidinone, 30 grams of 4,4-dimethyl-azetidinone and20 cc. of tetramethylene sulfone were slowly added dropwise whilevigorously stirring. The temperature was kept constant with cooling. Thereaction mixture became more and more viscous and, the dropwise additionbeing terminated, it solidified to a rubber-like gel. The gel wastriturated with water, washed with water and dried at 100 C. 30 grams ofa copolymer were obtained having a relative viscosity of 10, determinedat 20 C. with 1 gram of substance dissolved in 100 cc. of concentratedsulfuric acid.

EXAMPLE 7 A mixture of 30 grams of 4,4-dimethyl-azetidinone, 10 grams of4-methyl-azetidinone, 0.025 gram of oxalyl pyrrolidone and 100 cc. ofdimethyl sulfoxide was dropped over a period of 1 hour at 20 C. andwhile vigorously stirring into the dispersion of 1 gram of the potassiumsalt of pyrrolidone in 100 cc. of dimethyl sulfoxide. When the dropwiseaddition was terminated, the batch solidified. After trituration withwater and drying, 35 grams of polymer were obtained having a relativeviscosity of 13.0, determined at 20 C. with 1 gram of substancedissolved in 100 cc. of sulfuric acid. The product was soluble withoutresidue in phosphoric acid tris-dimethyl amide and the solution dried toa clear film. A homopolymer of 4- methyl-azetidinone was insoluble inphosphoric acid trisdimethyl amide.

Instead of dimethyl sulfoxide, phosphoric acid trisdimethyl amide couldbe used as solvent in the polymerization, the same result beingobtained.

EXAMPLE 3 A mixture of 7.5 grams of 4,4-dimethyl-azetidinone, 7.5 gramsof 4-methyl-4-propyl-azetidinone, 20 cc. of dimethyl sulfoxide and 0.03gram of oxalyl pyrrolidone was dropped over a period of 1 hour and at 20C. to a solution of 0.4 gram of the potassium salt of pyrrolidone and 1cc. of 4,4-dimethyl-azetidinone in 130 cc. of dimethyl sulfoxide. Thesolution became more and more viscous. After 4 hours water was stirredin, the batch was filtered off with suction and dried. 10 grams ofpolymer were obtained having a relative viscosity of 4.5, determined at20 C. with 1 gram of substance dissolved in 100 cc. of concentratedsulfuric acid. The product formed a clear solution in methanol. Ahomopolymer of 4,4-dimethylazetidinone was insoluble in methanol.

When N-methyl-pyrrolidone was used as solvent instead of dimethylsulfoxide, a polymer was obtained having a relative viscosity of 4.0.

EXAMPLE 9 A mixture of 7.5 grams of 4,4-dimethyl-azetidinone, 7.5 gramsof 4-methyl-4-propyl-azetidinone, grams of the unsaturated lactam ofFormula III and 20 cc. of dimethyl sulfoxide was dropped over a periodof 2 hours to a solution of 0.4 gram of the potassium salt ofpyrrolidone, 1 cc. of 4,4-dimethyl-azetidinone and 0.03 gram ofoxalyl-pyrrolidone in 180 cc. of dimethyl sulfoxide. 13 grams of acopolymer were obtained having a relative viscosity of 7.5, determinedat 20 C. with 1 gram of substance dissolved in 100 cc. of concentratedsulfuric acid. The product was clearly soluble in methanol. When allreaction components were rapidly mixed within 1 minute, the polymerobtained formed a strongly turbid solution in methanol. The homopolymersof 4,4-dimethyl-azetidinone and of the lactam of Formula III wereinsoluble in methanol.

EXAMPLE 10 A mixture of 150 grams of 3,4-dimethyl-azetidinone, 150 gramsof 4,4-dimethyl-azetidinone and 0.15 gram of oxalyl-pyrrolidone wasdropped over a period of 2 hours and at C. into the vigorously stirredemulsion of a solution of 6 cc. of 4,4-dimethyl-azetidinone, 3 grams ofthe potassium salt of pyrrolidone and 600 cc. of dimethyl sulfoxide in900 cc. of heavy gasoline of a boiling range of 160 to 180 C.,containing an emulsifying auxiliary 5 grams of polyethylene-propylenedimethyl sulfamide of the composition and 0.5 gram of polyisobutylene.The granular polymer was filtered off with suction, freed from thesolvents used by boiling it with water and dried at 100 C. 270 grams ofcopolymer were obtained having a relative viscosity of 11.5, determinedat 20 C. with 1 gram of substance dissolved in 100 cc. of concentratedsulfuric acid.

When dimethyl formamide was used instead of dimethyl sulfoxide assolvent, a polymer was obtained having a relative viscosity of 10.2.

EXAMPLE 11 A mixture of 90 grams of 4,4-dimethyl-azetidinone, 210- gramsof 4-methyl-azetidinone, 0.15 gram of oxalyl-pyrrolidone, 0.2 cc. ofwater and 300 cc. of isopropyl ether was dropped over a period of 1 hourat 20 C. into a vigorously stirred emulsion of a mixture of 600 cc. ofdimethyl sulfoxide, 12 cc. of 4,4-dimethyl-azetidinone, 6 grams of thepotassium salt of pyrrolidone, on the one hand, and 1.4 liters ofisopropyl ether, on the other, containing 3.7 grams ofpolyethylene-propylene dimethyl sulfamide as emulsifying auxiliary.After having boiled the granular reaction product with water, 270 gramsof copolymer were obtained having a relative viscosity of 9.8,determined at 20 C. with 1 gram of substance dissolved in 100 cc. ofconcentrated sulfuric acid. Structure analysis under X-rays anddifferential thermoanalysis indicated that the reaction product was atrue copolymer although the two monomeric beta-lactams polymerize withvery different speeds. When all reaction components were combined within1 minute, a non-uniform polymer was obtained.

8 EXAMPLE 12 A solution of 10 grams of 4-methyl-azetidinone, 5 grams of4-phenoxymethyl-4-methyl-azetidinone in 15 cc. of dodecyl benzene wasdropped at 20 C. and over a period of 1 hour into the emulsion of asolution of 0.4 gram of potassium salt of pyrrolidone, 1 cc. of4,4-dimethyl-azetidinone and 50 cc. of dimethyl sulfoxide in 75 cc. ofdodecyl benzene containing 0.6 gram of an emulsifying auxiliary as usedin Example 11. A copolymer was obtained in which the crystal lattice ofthe 4-methylazetidinone homopolymer did no longer occur.

EXAMPLE 13 A mixture of 15 grams of 4-vinyl-azetidinone, 15 grams of4-methyl-azetidinone and 30 cc. of isopropyl ether was dropped at 20 C.and over a period of 45 minutes into the emulsion of a solution of 70cc. of dimethyl sulfoxide, 0.6 cc. of 4,4-dimethyl-azetidinone, 0.3 gramof the potassium salt of pyrrolidone and 7 mg. of oxalyl-pyrrolidone incc. of isopropyl ether containing 0.5% of the emulsifying auxiliary usedin Example 12. After having eliminated the adhering solvents, 25 gramsof copolymer were obtained having a relative viscosity of 12.4,determined at 20 C. with 1 gram of substance dissolved in cc. ofconcentrated sulfuric acid. The copolymer had a melting point of 334 C.The homopolymers of the two individual components have higher meltingpoints. The copolymer was soluble in formic acid of 98% strength withoutresidue.

We claim:

1. In a process for producing polymers of betalactams having a hydrogenatom at the nitrogen atom thereof and having 0 to 4 substituents on thealpha and beta carbon atoms thereof containing up to 15 carbon atomswhich may comprise a ring including said alpha and beta carbon atoms,and up to 50% by weight of higher lactams, by ionic polymerization in apolymerization reaction medium comprising a solution or dispersion of abasic catalyst and at a temperature of -15 to C., the improvement whichcomprises feeding said lactam or lactams to said polymerization reactionmedium slowly at a rate substantially equal to the rate at which it isconsumed in the polymerization reaction.

2. In a process for producing polymers of betalactams having a hydrogenatom at the nitrogen atom thereof and having 0 to 4 substituents on thealpha and beta carbon atoms thereof containing up to 15 carbon atomswhich may comprise a ring including said alpha and beta carbon atoms,and up to 50% by Weight of higher lactams, by ionic polymerization in apolymerization reaction medium comprising a solution or dispersion of abasic catalyst and at a temperature of l5 to 120 C., the improvementwhich comprises feeding said lactam or lactams to said polymerizationreaction medium continuously at a rate sufliciently slow to avoid anysubstantial accumulation of unreacted monomer in the polymerizationreaction medium.

3. In a process for producing polymers of betalactams having a hydrogenatom at the nitrogen atom thereof and having 0 to 4 substituents on thealpha and beta carbon atoms thereof containing up to 15 carbon atomswhich may comprise a ring including said alpha and beta carbon atoms,and up to 50% by weight of higher lactams, by ionic polymerization in apolymerization reaction medium comprising a solution or dispersion of abasic catalyst and at a temperature of 15 to 120 C., the improvementwhich comprises feeding said lactam or lactams to said polymerizationreaction medium incrementally over a period of at least 45 minutes.

4. A process according to claim 1 wherein only one lactam is fed to thepolymerization reaction medium to produce a homopolymer.

5. A process according to claim 1 wherein a mixture of lactams is fed tothe polymerization reaction mixture to produce a copolymer.

6. A process according to claim 1 wherein a solution of the basiccatalyst is used.

7. A process according to claim 6 wherein the catalyst solution isemulsified in a different second solvent which when mixed with thesolvent of the catalyst forms two phases.

8. A process according to claim 7 wherein the second solvent iscompletely miscible with the beta-lactam to be polymerized.

9. A process according to claim 6 wherein the inert solvent of thecatalyst is at least one solvent selected from the group consisting ofdimethyl sulfoxide, tetramethylene sulfone, phosphoric acidtris-dimethyl amide, dimethyl formamide and N-methyl-pyrrolidone.

10. A process according to claim 7 wherein the inert solvent of thecatalyst is at least one solvent selected from the group consisting ofdimethyl sulfoxide and tetramethylene sulfone.

11. A process according to claim 7 wherein the inert solvent of thecatalyst is at least one solvent selected from the group consisting ofdimethyl formamide and N-methyl-pyrrolidone and the second solvent forsaid catalyst solution is at least one solvent selected from the groupconsisting of aliphatic and cycloaliphatic hydrocarbons having to 24carbon atoms in the molecule.

12. A process according to claim 8 wherein the inert solvent of thecatalyst is at least one solvent selected from the group consisting ofdimethyl sulfoxide, tetramethylene sulfone, phosphoric acidtris-dimethyl amide, dimethyl 'formamide and N-methyl-pyrrolidoneand thesecond solvent of said catalyst solution is at least one solventselected from the group consisting of aliphatic ethers having 1 to 5ether oxygen atoms and 4 to 24 carbon atoms in the molecule, araliphaticethcrs having 1 to 3 ether oxygen atoms, 6 to 24 aliphatically boundcarbon atoms and 1 to 3 phenyl rings in the molecule, and araliphatichydrocarbons with 1 to 3 phenyl rings and 3 to 24 aliphatically boundcarbon atoms in the molecule.

13. A process according to claim 1 wherein a dispersion of the basiccatalyst is used.

14. A process according to claim 13 wherein the catalyst dispersion isemulsified in a different second solvent which when mixed with thesolvent of the catalyst forms two phases.

15. A process according to claim 13 wherein the sec 0nd solvent iscompletely miscible with the beta-lactam to be polymerized.

16. A process for producing polymers of beta-lactams having a hydrogenatom at the nitrogen atom thereof and having 0 to 4 substituents on thealpha and beta carbon atoms thereof containing up to 15 carbon atomswhich may comprise a ring including said alpha and beta carbon atoms,and up to by weight of higher lactams, said process comprisingestablishing a polymerization reaction medium comprising an inertsolvent solution of a basic catalyst, said catalyst solution beingemulsified in a different second solvent which when mixed with thesolvent of the catalyst forms two phases, feeding one or more of saidbeta-lactams to said polymerization reaction medium and maintaining saidreaction medium at l5 to C. to cause said beta-lactams to polymerize.

17. A process according to claim 16 wherein the betalactams to bepolymerized are completely miscible with said second solvent.

18. A process for producing polymers of beta-lactarns having a hydrogenatom at the nitrogen atom thereof and having 0 to 4 substituents on thealpha and beta carbon atoms thereof containing up to 15 carbon atomswhich may comprise a ring including said alpha and beta carbon atoms,and up to 50% by Weight of higher lactams, said process comprisingestablishing a polymerization reaction medium comprising an inertsolvent dispersion of a basic catalyst, said catalyst dispersion beingemulsified in a different second solvent which when mixed with thesolvent of the catalyst dispersion forms two phases, feeding one or moreof said beta-lactams slowly to said polymerization reaction medium andmaintaining said reaction medium at -1S to 120 C. to cause saidbeta-lactams to polymerize.

19. A process according to claim 18 wherein the betalactams to bepolymerized are completely miscible with said second solvent.

References Cited UNITED STATES PATENTS 3,417,163 12/1968 Beermann et a1260-857 WILLIAM H. SHORT, Primary Examiner L. M. PHYNES, AssistantExaminer US. Cl. X.R.

